1. Field of the Invention
This invention relates to the production of light olefins, hydrocarbons boiling in the gasoline boiling range or the distillate boiling range and mixtures thereof from lower aliphatic alcohols, related and other oxygenates, and mixtures thereof. More particularly, it relates to the catalytic conversion of an alcohol or oxygenate-containing feed to olefins and/or C.sub.5 + hydrocarbons. This invention especially relates to the conversion of C.sub.1 -C.sub.3 monohydric alcohols, related oxygenates and/or Fisher-Tropsch oxygenates to light olefins, gasoline boiling range hydrocarbons and/or distillate boiling range hydrocarbons in a bed of ZSM-5 type zeolite catalyst operating in the turbulent fluidization regime.
2. Description of the Prior Art
The growing demand for fuels and light petroleum products, including light olefin gases, and the growing shortage of crude oil supply, has resulted in a continuing strong interest in tapping alternate raw material sources from which to obtain the desired light hydrocarbon products.
In recent years, the patent art has disclosed that alcohols and related oxygenates, which may be obtained from coal, natural gas or biomass, can be converted to more complex hydrocarbons, including gasoline boiling hydrocarbons, by utilizing a novel group of zeolites, exemplified by ZSM-5 zeolite. In one commercial aspect the process is employed as part of the conversion of natural gas to gasoline. Here natural gas is steam reformed to synthesis gas which in turn is converted to methanol. The methanol is then converted to gasoline employing Mobil Oil Corporation's MTG (methanol to gasoline) process. The MTG process is disclosed in the patent art, including, for example, U.S. Pat. Nos. 3,894,103; 3,894,104; 3,894,107; 4,035,430 and 4,058,576. U.S. Pat. No. 3,894,102 discloses the conversion of synthesis gas to gasoline.
The conversion of lower monohydric alcohols to gasoline by the catalytic action of ZSM-5 type zeolites is highly exothermic. To control this exothermic heat, a number of patentees have employed fluidized catalyst techniques which were developed heretofore, principably in the petroleum industry. Fluidization methods have been usefully employed in the cracking of gas oils where the powdered catalyst was used to transfer heat, developed during the regeneration of the catalyst in a fluidized bed, to another fluidized bed of catalyst to effect the endothermic cracking of the gas oil.
A number of commonly assigned patents and patent applications disclose the use of fluidized bed techniques not only to control the heat released in the conversion of alcohols to gasoline but also, because of the intimate contact between reactants and catalyst provided by the fluidized catalyst, to improve product selectivity and catalyst life. However, the nature of the fluidized catalyst bed employed promotes the growth of bubbles of reactant gases and the backmixing of the gasiform materials, both of which are undesirable. These prior art patents have addressed these problems in a variety of ways. Thus, U.S. Pat. No. 4,071,573 of Owen et al. discloses the use of horizontally disposed grid means, such as wire mesh screens or heat exchanger means, in a dilute phase catalyst riser reactor to disperse reactant or product gas bubbles as the catalyst-reactant suspension passes upwardly through the riser. A plurality of vertical baffles is provided in the dense phase fluid catalyst bed disclosed in U.S. Pat. No. 4,197,418 of Lee et al. which are said to restrict upflowing reactant bubble growth so as not to exceed about six inches and to provide substantial plug flow conditions. U.S. Pat. Nos. 4,238,631 and 4,251,484 of Daviduk et al. disclose a dense fluidized bed reactor for methanol conversion provided with a plurality of vertical heat exchanger tubes and vertical open end baffle tubes which are spaced to provide a flow path having a hydraulic diameter of four to eight inches when the reactants are in contact with the fluid mass of catalyst particles. Commonly assigned patent application Ser. No. 400,203, filed July 20, 1982 discloses the use of a dense fluidized bed reactor provided with a plurality of horizontally disposed baffles which result in a increase in the conversion efficiency as compared to a unbaffled or vertically baffled dense fluidized bed reactor. The entire contents of these four commonly assigned patents are incorporated herein by reference.
These prior art patents are concerned with various types of horizontal and vertical baffles for dispersing gas bubbles in the fluidized bed. Specifically, Lee et al. is concerned with breaking up bubbles to not more than six inches, preferably not more than four inches while Daviduk et al's U.S. Pat. No. 4,251,484 speaks of restricting gas bubble growth to less than twenty-four inches, preferably not to exceed eight inches. The baffles in the reactor of Daviduk et al. provide a hydraulic diameter of the vertical passageways of four to eight inches.
It is an object of the invention to improve the prior art processes which employ dense fluid bed technology for the conversion of lower alcohols and oxygenates to light olefins, gasoline boiling hydrocarbons and/or distillate boiling range hydrocarbons.
It is another object of this invention to provide a process for the conversion of lower alcohols and oxygenates to light olefins, gasoline boiling range hydrocarbons and/or distillate boiling range hydrocarbons by means of a fluidized ZSM-5 type zeolite catalyst.
It is a further object of this invention to provide a process for the conversion of lower alcohols and oxygenates to light olefins, gasoline and/or distillate fuels by means of a ZSM-5 type zeolite catalyst in a fluidized system which provide the gaseous reaction mixture in a series of bubbles which are small, random and shortlived thereby providing good contact between the gaseous reactants and the catalyst particules.
The achievement of these and other objects will be apparent from the following description of the subject invention.